JP2000282435A - Breakeater structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent increase of wave height caused by a resonance phenomenon in a harbor so as to prevent rolling/pitching of a ship by forming a hole communicating the outside of the harbor with the inside thereof at a lower portion of a breakwater. SOLUTION: A breakwater 2 is formed to extende from a quay 1. The breakwater 2 is formed with a harbor port 3 and a bottomed caisson 7 is inserted into at least a part of the breakwater 2. Water from the inside of the harbor 5 moves to the outside 6 of the harbor 5 through a hole at a lower portion of the caisson 7 and a part of long cyclic component energy of wave in the harbor 5 is transmitted to the outside 6 through the hole. Since waves comming from the outside 6 are almost short cyclic components, almost the wave energy is in the vicinity of a water level so that the energy is blocked at an upper part of the bottomed caisson 7. Accordingly, the purpose is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a breakwater structure, and more particularly to a breakwater structure using a perforated caisson.

[0002]

2. Description of the Related Art With the recent increase in size of ships, long-period fluctuations of the mooring ships have resulted in serious problems such as obstacles in cargo handling of the moored ships and breakage of mooring lines. A moored ship has a natural period. If the natural period of the moored ship coincides with the period of waves acting as an external force, a large hull sway occurs. On the other hand, harbors also have a natural period corresponding to the shape and scale, and when the natural period and the period of the waves that have entered the harbor match, resonance occurs, and the wave inside the port rises many times as high as the wave outside the port. May be. In general, the natural period of a port is several tens of seconds to several tens of minutes, whereas for large vessels of the tens of thousands of tons, the natural period of sway is about several minutes. There is a danger of doing it.

When the natural period of a port is about several minutes and coincides with the natural period of a moored ship, the motion of the moored ship becomes large, and some countermeasures must be taken. For the long-period component of the wave whose natural period is about several minutes, measures such as installation of wave breakers that deal with ordinary waves have no effect,
At present, temporary measures are taken, for example, by stiffening the mooring lines and shifting the natural period of ship sway from the natural period of the port.

[0004]

As described above, the prior art for controlling the resonance of waves in a harbor can be dealt with by setting an appropriate harbor layout so as not to cause resonance in a newly constructed harbor. However, due to problems such as site restrictions, there is a limit to how to deal with port layout.

[0005] In the case of an existing port, measures such as hardening the mooring line or extending the offshore breakwater are taken. However, when the mooring line is hardened, the mooring line is likely to be cut. Also, it is only a temporary measure. The extension of the offshore breakwater reduces the energy of waves entering the port, so it is effective to maintain the calmness of normal waves in the port.However, when the wave height in the port increases due to resonance, waves from the port There is also a danger of increasing the wave height because it is difficult to get out.

The present invention has been made to eliminate the above disadvantages.

[0007]

The wavebreak structure of the present invention comprises:
A hole communicating at least part of the breakwater between the outside and the inside of the harbor is formed to transmit only the long-period component of the wave to prevent an increase in wave height due to the resonance phenomenon inside the harbor. .

[0008] The hole is formed in a caisson interposed in the breakwater.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a quay, 2 is a breakwater extending from the quay 1, 3 is a port formed in the breakwater 2, 4
Indicates a ship, 5 indicates a port, and 6 indicates a port. In the present invention, a perforated caisson 7 is inserted into at least a part of the breakwater 2.

As shown in FIG. 2, the perforated caisson 7 includes a caisson body 8 made of cubic concrete or the like.
The caisson body 8 has a hole portion 9 penetrating from the outer surface of the lower port to the inner surface of the lower port.

Since the breakwater structure of the present invention is configured as described above, water particles from the port 5 move to the port outside 6 through the lower hole 9 of the caisson body 8 as shown in FIG. Become like

In general, as shown in FIG. 4A, the movement of water particles by waves is such that in the case of a long-period component generated by resonance in a port, water particles move at the same amplitude on both the water surface and the seabed, but most of the components of ordinary waves In the case of an existing short-period component, water particles on the water surface move as shown in FIG. 4B, but water particles on the sea bottom hardly move. That is, most of the energy of the short-period component exists near the water surface, whereas the energy of the long-period component is distributed almost uniformly from the water surface to the sea floor.

Therefore, according to the breakwater structure of the present invention, part of the energy of the long-period component of the wave in the harbor 5 propagates through the hole 9 of the caisson body 8 to the outside of the harbor 6. . On the other hand, since most of the waves arriving from the port 6 are short-period components, most of the energy of the waves is near the water surface and is shielded at the upper part of the perforated caisson 7, and most of the energy of the waves is perforated caisson 7. Cannot be transmitted.

[0015]

As described above, according to the breakwater structure of the present invention, by installing a perforated caisson at an appropriate position on a breakwater in a harbor, the long-period component that causes resonance in the harbor can be reduced. Since the light is transmitted to the outside and does not cause resonance in the harbor, vibration in the direction along the quay where the ship is moored does not occur, and there is a great advantage that the movement of the ship can be suppressed.

[Brief description of the drawings]

FIG. 1 is an explanatory plan view of a wavebreak structure of the present invention.

FIG. 2 is a perspective view of a perforated caisson in the wavebreak structure of the present invention.

FIG. 3 is an explanatory diagram of a perforated caisson shown in FIG. 3;

FIG. 4A is an explanatory diagram of movement of water particles in a case of a long-period component.

FIG. 4B is an explanatory diagram of movement of water particles in the case of a short-period component.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wharf 2 Breakwater 3 Harbor 4 Ship 5 Port inside 6 Outside port 7 Perforated caisson 8 Caisson main body 9 Hole part

Claims (2)

[Claims] At least a part of the breakwater is formed with a hole communicating with the outside and inside of the harbor at a lower portion of the breakwater so as to transmit only a long-period component of the wave to prevent an increase in wave height due to a resonance phenomenon in the harbor. A wave-proof structure characterized by the above-mentioned. 2. The breakwater structure according to claim 1, wherein the hole is formed in a caisson interposed between the breakwaters.